Championship kha'zix chroma's & borders

I know that championship kha'zix and the team chromas have their own borders, but if we craft the standard border, why don't we get that on all the chroma's for which we do not own the team border?

I had some spare tokens and thought 'well, why not get the border', boy was i wrong, turns out it only works for the standard skin, it doesn't even work on the golden chroma.

Why couldn't riot enable the standard border on all chroma's apart from the ones for which you OWN the team border? It makes way more sense, right now i just have thrown 300 tokens out of the window, could as well have bought key fragments then as i'm still sitting on 30 chests from season 7.

What is the exact reason that it's handled like this?